Dawn mission Archives

August 23, 2015March 1, 2022 by Matt Williams

What is the Asteroid Belt?

Artist concept of the asteroid belt. Credit: NASA

In the 18th century, observations made of all the known planets (Mercury, Venus, Earth, Mars, Jupiter, and Saturn) led astronomers to discern a pattern in their orbits. Eventually, this led to the Titius–Bode Law, which predicted the amount of space between the planets. In accordance with this law, there appeared to be a discernible gap between the orbits of Mars and Jupiter, and investigation into it led to a major discovery.

In addition to several larger objects being observed, astronomers began to notice countless smaller bodies also orbiting between Mars and Jupiter. This led to the creation of the term “asteroid”, as well as “Asteroid Belt” once it became clear just how many there were. Since that time, the term has entered common usage and become a mainstay of our astronomical models.

Discovery:

In 1800, hoping to resolve the issue created by the Titius-Bode Law, astronomer Baron Franz Xaver von Zach recruited 24 of his fellow astronomers into a club known as the “United Astronomical Society” (sometimes referred to the as “Stellar Police”). At the time, its ranks included famed astronomer William Herschel, who had discovered Uranus and its moons in the 1780s.

Ironically, the first astronomer to make a discovery in this regions was Giuseppe Piazzi – the chair of astronomy at the University of Palermo – who had been asked to join the Society but had not yet received the invitation. On January 1st, 1801, Piazzi observed a tiny object in an orbit with the exact radius predicted by the Titius-Bode law.

Ceres (left, Dawn image) compared to Tethys (right, Cassini image) at comparative scale sizes. (Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA and NASA/JPL-Caltech/SSI. Comparison by J. Major.) — *Ceres (left, Dawn image) compared to Tethys (right, Cassini image) at comparative scale sizes. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA and NASA/JPL-Caltech/SSI. Comparison by J. Major.*

Initially, he believed it to be a comet, but ongoing observations showed that it had no coma. This led Piazzi to consider that the object he had found – which he named “Ceres” after the Roman goddess of the harvest and patron of Sicily – could, in fact, be a planet. Fifteen months later, Heinrich Olbers ( a member of the Society) discovered a second object in the same region, which was later named 2 Pallas.

In appearance, these objects seemed indistinguishable from stars. Even under the highest telescope magnifications, they did not resolve into discs. However, their rapid movement was indicative of a shared orbit. Hence, William Herschel suggested that they be placed into a separate category called “asteroids” – Greek for “star-like”.

By 1807, further investigation revealed two new objects in the region, 3 Juno and 4 Vesta; and by 1845, 5 Astraea was found. Shortly thereafter, new objects were found at an accelerating rate, and by the early 1850s, the term “asteroids” gradually came into common use. So too did the term “Asteroid Belt”, though it is unclear who coined that particular term. However, the term “Main Belt” is often used to distinguish it from the Kuiper Belt.

One hundred asteroids had been located by mid-1868, and in 1891 the introduction of astrophotography by Max Wolf accelerated the rate of discovery even further. A total of 1,000 asteroids were found by 1921, 10,000 by 1981, and 100,000 by 2000. Modern asteroid survey systems now use automated means to locate new minor planets in ever-increasing quantities.

*The asteroids of the inner Solar System and Jupiter: The donut-shaped asteroid belt is located between the orbits of Jupiter and Mars. Credit: Wikipedia Commons*

Structure:

Despite common perceptions, the Asteroid Belt is mostly empty space, with the asteroids spread over a large volume of space. Nevertheless, hundreds of thousands of asteroids are currently known, and the total number ranges in the millions or more. Over 200 asteroids are known to be larger than 100 km in diameter, and a survey in the infrared wavelengths has shown that the asteroid belt has 0.7–1.7 million asteroids with a diameter of 1 km (0.6 mi) or more.

Located between Mars and Jupiter, the belt ranges from 2.2 to 3.2 astronomical units (AU) from the Sun and is 1 AU thick. Its total mass is estimated to be 2.8×10²¹ to 3.2×10²¹ kilograms – which is equivalent to about 4% of the Moon’s mass. The four largest objects – Ceres, 4 Vesta, 2 Pallas, and 10 Hygiea – account for half of the belt’s total mass, with almost one-third accounted for by Ceres alone.

The main (or core) population of the asteroid belt is sometimes divided into three zones, which are based on what is known as Kirkwood Gaps. Named after Daniel Kirkwood, who announced in 1866 the discovery of gaps in the distance of asteroids, these describe the dimensions of an asteroid’s orbit based on its semi-major axis.

Within this scheme, there are three zones. Zone I lies between the 4:1 resonance and 3:1 resonance Kirkwood gaps, which are 2.06 and 2.5 AU from the Sun respectively. Zone II continues from the end of Zone I out to the 5:2 resonance gap, which is 2.82 AU from the Sun. Zone III extends from the outer edge of Zone II to the 2:1 resonance gap at 3.28 AU.

The asteroid belt may also be divided into the inner and outer belts, with the inner belt formed by asteroids orbiting nearer to Mars than the 3:1 Kirkwood gap (2.5 AU), and the outer belt formed by those asteroids closer to Jupiter’s orbit.

The asteroids that have a radius of 2.06 AU from the Sun can be considered the inner boundary of the asteroid belt. Perturbations by Jupiter send bodies straying there into unstable orbits. Most bodies formed inside the radius of this gap were swept up by Mars (which has an aphelion at 1.67 AU) or ejected by its gravitational perturbations in the early history of the Solar System.

The temperature of the Asteroid Belt varies with the distance from the Sun. For dust particles within the belt, typical temperatures range from 200 K (-73 °C) at 2.2 AU down to 165 K (-108 °C) at 3.2 AU. However, due to rotation, the surface temperature of an asteroid can vary considerably as the sides are alternately exposed to solar radiation and then to the stellar background.

Composition:

Much like the terrestrial planets, most asteroids are composed of silicate rock while a small portion contains metals such as iron and nickel. The remaining asteroids are made up of a mix of these, along with carbon-rich materials. Some of the more distant asteroids tend to contain more ices and volatiles, which includes water ice.

Vesta seen from the Earth-orbit based Hubble Space Telescope in 2007 (left) and up close with the Dawn spacecraft in 2011. Hubble Credit: NASA, ESA, and L. McFadden (University of Maryland). Dawn Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA. Photo Combination: Elizabeth Howell

The Main Belt consists primarily of three categories of asteroids: C-type, or carbonaceous asteroids; S-type, or silicate asteroids; and M-type, or metallic asteroids. Carbonaceous asteroids are carbon-rich, dominate the belt’s outer regions, and comprise over 75% of the visible asteroids. Their surface composition is similar to that of carbonaceous chondrite meteorites while their spectra is similar to what the early Solar System’s is believed to be.

S-type (silicate-rich) asteroids are more common toward the inner region of the belt, within 2.5 AU of the Sun. These are typically composed of silicates and some metals, but not a significant amount of carbonaceous compounds. This indicates that their materials have been modified significantly over time, most likely through melting and reformation.

M-type (metal-rich) asteroids form about 10% of the total population and are composed of iron-nickel and some silicate compounds. Some are believed to have originated from the metallic cores of differentiated asteroids, which were then fragmented from collisions. Within the asteroid belt, the distribution of these types of asteroids peaks at a semi-major axis of about 2.7 AU from the Sun.

There’s also the mysterious and relatively rare V-type (or basaltic) asteroids. This group takes their name from the fact that until 2001, most basaltic bodies in the Asteroid Belt were believed to have originated from the asteroid Vesta. However, the discovery of basaltic asteroids with different chemical compositions suggests a different origin. Current theories of asteroid formation predict that the V-type asteroids should be more plentiful, but 99% of those that have been predicted are currently missing.

Families and Groups:

Approximately one-third of the asteroids in the asteroid belt are members of an asteroid family. These are based on similarities in orbital elements – such as semi-major axis, eccentricity, orbital inclinations, and similar spectral features, all of which indicate a common origin. Most likely, this would have involved collisions between larger objects (with a mean radius of ~10 km) that then broke up into smaller bodies.

This artist's conception shows how families of asteroids are created. Credit: NASA/JPL-Caltech — *This artist’s conception shows how families of asteroids are created. Credit: NASA/JPL-Caltech*

Some of the most prominent families in the asteroid belt are the Flora, Eunomia, Koronis, Eos, and Themis families. The Flora family, one of the largest with more than 800 known members, may have formed from a collision less than a billion years ago. Located within the inner region of the Belt, this family is made up of S-type asteroids and accounts for roughly 4-5% of all Belt objects.

The Eunomia family is another large grouping of S-type asteroids, which takes its name from the Greek goddess Eunomia (goddess of law and good order). It is the most prominent family in the intermediate asteroid belt and accounts for 5% of all asteroids.

The Koronis family consists of 300 known asteroids which are thought to have been formed at least two billion years ago by a collision. The largest known, 208 Lacrimosa, is about 41 km (25 mi) in diameter, while an additional 20 more have been found that are larger than 25 km in diameter.

The Eos (or Eoan) family is a prominent family of asteroids that orbit the Sun at a distance of 2.96 – 3.03 AUs, and are believed to have formed from a collision 1-2 billion years ago. It consists of 4,400 known members that resemble the S-type asteroid category. However, the examination of Eos and other family members in the infrared show some differences with the S-type, thus why they have their own category (K-type asteroids).

Asteroids we've seen up close show cratered surfaces similar to yet different from much of the cratering on comets. Credit: NASA — *Asteroids we’ve seen up close show cratered surfaces similar to yet different from much of the cratering on comets. Credit: NASA*

The Themis asteroid family is found in the outer portion of the asteroid belt, at a mean distance of 3.13 AU from the Sun. This core group includes the asteroid 24 Themis (for which it is named) and is one of the more populous asteroid families. It is made up of C-type asteroids with a composition believed to be similar to that of carbonaceous chondrites and consists of a well-defined core of larger asteroids and a surrounding region of smaller ones.

The largest asteroid to be a true member of a family is 4 Vesta. The Vesta family is believed to have formed as the result of a crater-forming impact on Vesta. Likewise, the HED meteorites may also have originated from Vesta as a result of this collision.

Along with the asteroid bodies, the asteroid belt also contains bands of dust with particle radii of up to a few hundred micrometers. This fine material is produced, at least in part, from collisions between asteroids, and by the impact of micrometeorites upon the asteroids. Three prominent bands of dust have been found within the asteroid belt – which have similar orbital inclinations as the Eos, Koronis, and Themis asteroid families – and so are possibly associated with those groupings.

Origin:

Originally, the Asteroid Belt was thought to be the remnants of a much larger planet that occupied the region between the orbits of Mars and Jupiter. This theory was originally suggested by Heinrich Olbders to William Herschel as a possible explanation for the existence of Ceres and Pallas. However, this hypothesis has since fallen out of favor for a number of reasons.

Artist's impression of the early Solar System, where collision between particles in an accretion disc led to the formation of planetesimals and eventually planets. Credit: NASA/JPL-Caltech — *Artist’s impression of the early Solar System, where collisions between particles in an accretion disc led to the formation of planetesimals and eventually planets. Credit: NASA/JPL-Caltech*

First, there is the amount of energy it would have required to destroy a planet, which would have been staggering. Second, there is the fact that the entire mass of the Belt is only 4% that of the Moon. Third, the significant chemical differences between the asteroids do not point towards them having been once part of a single planet.

Today, the scientific consensus is that, rather than fragmenting from a progenitor planet, the asteroids are remnants from the early Solar System that never formed a planet at all. During the first few million years of the Solar System’s history, when gravitational accretion led to the formation of the planets, clumps of matter in an accretion disc coalesced to form planetesimals. These, in turn, came together to form planets.

However, within the region of the Asteroid Belt, planetesimals were too strongly perturbed by Jupiter’s gravity to form a planet. These objects would continue to orbit the Sun as before, occasionally colliding and producing smaller fragments and dust.

During the early history of the Solar System, the asteroids also melted to some degree, allowing elements within them to be partially or completely differentiated by mass. However, this period would have been necessarily brief due to their relatively small size, and likely ended about 4.5 billion years ago, in the first tens of millions of years of the Solar System’s formation.

Though they are dated to the early history of the Solar System, the asteroids (as they are today) are not samples of its primordial self. They have undergone considerable evolution since their formation, including internal heating, surface melting from impacts, space weathering from radiation, and bombardment by micrometeorites. Hence, the Asteroid Belt today is believed to contain only a small fraction of the mass of the primordial belt.

Computer simulations suggest that the original asteroid belt may have contained as much mass as Earth. Primarily because of gravitational perturbations, most of the material was ejected from the belt a million years after its formation, leaving behind less than 0.1% of the original mass. Since then, the size distribution of the asteroid belt is believed to have remained relatively stable.

When the asteroid belt was first formed, the temperatures at a distance of 2.7 AU from the Sun formed a “snow line” below the freezing point of water. Essentially, planetesimals formed beyond this radius were able to accumulate ice, some of which may have provided a water source of Earth’s oceans (even more so than comets).

Exploration:

The asteroid belt is so thinly populated that several unmanned spacecraft have been able to move through it; either as part of a long-range mission to the outer Solar System, or (in recent years) as a mission to study larger Asteroid Belt objects. In fact, due to the low density of materials within the Belt, the odds of a probe running into an asteroid are now estimated at less than one in a billion.

The first spacecraft to make a journey through the asteroid belt was the Pioneer 10 spacecraft, which entered the region on July 16th, 1972. As part of a mission to Jupiter, the craft successfully navigated through the Belt and conducted a flyby of Jupiter (which culminated in December of 1973) before becoming the first spacecraft to achieve escape velocity from the Solar System.

At the time, there were concerns that the debris would pose a hazard to the Pioneer 10 space probe. But since that mission, 11 additional spacecraft passed through the Asteroid Belt without incident. These included Pioneer 11, Voyager 1 and 2, Ulysses, Galileo, NEAR, Cassini, Stardust, New Horizons, the ESA’s Rosetta, and most recently, the Dawn spacecraft.

For the most part, these missions were part of missions to the outer Solar System, where opportunities to photograph and study asteroids were brief. Only the Dawn, NEAR and JAXA’s Hayabusa missions have studied asteroids for a protracted period in orbit and at the surface. Dawn explored Vesta from July 2011 to September 2012 and is currently orbiting Ceres (and sending back many interesting pictures of its surface features).

And someday, if all goes well, humanity might even be in a position to begin mining the asteroid belt for resources – such as precious metals, minerals, and volatiles. These resources could be mined from an asteroid and then used in space of in-situ utilization (i.e. turning them into construction materials and rocket propellant), or brought back to Earth.

It is even possible that humanity might one day colonize larger asteroids and establish outposts throughout the Belt. In the meantime, there’s still plenty of exploring left to do, and quite possibly millions of more objects out there to study.

We have written many articles about the asteroid belt for Universe Today. Here’s Where Do Asteroids Come From?, Why the Asteroid Belt Doesn’t Threaten Spacecraft, and Why isn’t the Asteroid Belt a Planet?.

Also, be sure to learn which is the Largest Asteroid in the Solar System, and about the asteroid named after Leonard Nimoy. And here’s 10 Interesting Facts about Asteroids.

We also have many interesting articles about the Dawn spacecraft’s mission to Vesta and Ceres, and asteroid mining.

To learn more, check out NASA’s Lunar and Planetary Science Page on asteroids, and the Hubblesite’s News Releases about Asteroids.

Astronomy Cast also some interesting episodes about asteroids, like Episode 55: The Asteroid Belt and Episode 29: Asteroids Make Bad Neighbors.

Sources:

August 11, 2015May 23, 2017 by Matt Williams

The Dwarf Planet Ceres

A view of Ceres in natural colour, pictured by the Dawn spacecraft in May 2015. Credit: NASA/ JPL/Planetary Society/Justin Cowart

The Asteroid Belt is a pretty interesting place. In addition to containing between 2.8 and 3.2 quintillion metric tons of matter, the region is also home to many minor planets. The largest of these, known as Ceres, is not only the largest minor planet in the Inner Solar System, but also the only body in this region to be designated as a “dwarf planet” by the International Astronomical Union (IAU).

Due to its size and shape, when it was first observed, Ceres was thought to be a planet. While this belief has since been revised, Ceres is alone amongst objects in the Asteroid Belt in that it is the only object massive enough to have become spherical in shape. And like most of the dwarf planets in our Solar System, its status remains controversial, and our knowledge of it limited.

Discovery and Naming:

Ceres was discovered by Giuseppe Piazzi on January 1st, 1801, while searching for zodiacal stars. However, the existence of Ceres had been predicted decades before by Johann Elert Bode, a German astronomer who speculated that there had to be a planet between Mars and Jupiter. The basis for this assumption was the now defunct Bode-Titus law, which was first proposed by Johann Daniel Titius in 1766.

This law stated that there existed a regular pattern in the semi-major axes of the orbits of known planets, the only exception of which was the large gap between Mars and Jupiter. In an attempt to resolve this, in 1800, German astronomer Franz Xaver von Zach sent requests to twenty-four experienced astronomers (dubbed the “Celestial Police”) to combine their their efforts to located this missing planet.

One of these astronomers was Giuseppe Piazzi at the Academy of Palermo, who had made the discovery shortly before his invitation to join the group had arrived. At the time of his discovery, he mistook it for a comet, but subsequent observations led him to declare that it could be something more. He officially shared his observations with friends and colleagues by April of 1801, and sent the information to von Zach to be published in September.

Unfortunately, due to its change in its apparent position, Ceres was too close to the Sun’s glare to be visible to astronomers. It would not be until the end of the year that it would be spotted again, thanks in large part to German astronomer Carl Freidrich Gauss and the predictions he made of its orbit. On December 31st, von Zach and his colleague Heinrich W.M. Olbers found Ceres near the position predicted by Gauss, and thus recovered it.

Piazzi originally suggesting naming his discovery Cerere Ferdinandea, after the Roman goddess of agriculture Ceres (Cerere in Italian) and King Ferdinand of Sicily. The name Ferdinand was dropped in other nations, but Ceres was eventually retained. Ceres was also called Hera for a short time in Germany; whereas in Greece, it is still called Demeter after the Greek equivalent of the Roman goddess Ceres.

Classification:

The classification of Ceres has changed more than once since its discovery, and remains the subject of controversy. For example, Johann Elert Bode – a contemporary of Piazzi – believed Ceres to be the “missing planet” he had proposed to exist between Mars and Jupiter. Ceres was assigned a planetary symbol, and remained listed as a planet in astronomy books and tables (along with 2 Pallas, 3 Juno, and 4 Vesta) until the mid-19th century.

Ceres compared to asteroids visited to date, including Vesta, Dawn's mapping target in 2011. Image by NASA/ESA. Compiled by Paul Schenck. — *Ceres compared to asteroids visited to date, including Vesta, Dawn’s mapping target in 2011. Credit: NASA/ESA/Paul Schenck.*

As other objects were discovered in the neighborhood of Ceres, it was realized that Ceres represented the first of a new class of objects. In 1802, with the discovery of 2 Pallas, William Herschel coined the term asteroid (“star-like”) for these bodies. As the first such body to be discovered, Ceres was given the designation 1 Ceres under the modern system of minor-planet designations.

By the 1860s, the existence of a fundamental difference between asteroids such as Ceres and the major planets was widely accepted, though a precise definition of “planet” was never formulated. The 2006 debate surrounding Eris, Pluto, and what constitutes a planet led to Ceres being considered for reclassification as a planet.

The definition that was adopted on August 24th, 2006 carried the requirements that a planet have sufficient mass to assume hydrostatic equilibrium, be in orbit around a star and not be a satellite, and have cleared the neighborhood around its orbit. As it is, Ceres does not dominate its orbit, but shares it with the thousands of other asteroids, and constitutes only about a third of the mass of the Asteroid Belt. Bodies like Ceres that met some of these qualification, but not all, were instead classified as “dwarf planets”.

In addition to the controversy surrounding the use of this term, there is also the question of whether or not Ceres status as a dwarf planet means that it can no longer be considered an asteroid. The 2006 IAU decision never addressed whether Ceres is an asteroid or not. In fact, the IAU has never defined the word ‘asteroid’ at all, having preferred the term ‘minor planet’ until 2006, and the terms ‘small Solar System body’ and ‘dwarf planet’ thereafter.

Size, Mass and Orbit:

Early observations of Ceres were only able to calculate its size to within an order of magnitude. In 1802, English astronomer William Herschel underestimated its diameter as 260 km, whereas in 1811 Johann Hieronymus Schröter overestimated it as 2,613 km. Current estimates place its mean radius at 473 km, and its mass at roughly 9.39 × 10²⁰ kg (the equivalent of 0.00015 Earths or 0.0128 Moons).

Size comparison of Vesta, Eros and Ceres and Eros — *Size comparison of Vesta, Eros and Ceres. Credit: NASA/JPL*

With this mass, Ceres comprises approximately a third of the estimated total mass of the asteroid belt (which is in turn approximately 4% of the mass of the Moon). The next largest objects are Vesta, Pallas and Hygiea, which have mean diameters of more than 400 km and masses of 2.6 x 10²⁰ kg, 2.11 x 10²⁰kg, and 8.6 ×10¹⁹ kg respectively. The mass of Ceres is large enough to give it a nearly spherical shape, which makes it unique amongst objects and minor planets in the Asteroid Belt.

Ceres follows a slightly inclined and moderately eccentric orbit, ranging from 2.5577 AU (382.6 million km) from the Sun at perihelion and 2.9773 AU (445.4 million km) at aphelion. It has an orbital period of 1,680 Earth days (4.6 years) and takes 0.3781 Earth days (9 hours and 4 minutes) to complete a sidereal rotation.

Composition and Atmosphere:

Based on its size and density (2.16 g/cm³), Ceres is believed to be differentiated between a rocky core and an icy mantle. Based on evidence provided by the Keck telescope in 2002, the mantle is estimated to be 100 km-thick, and contains up to 200 million cubic km of water – which is more fresh water than exists on Earth. Infrared data on the surface also suggests that Ceres may have an ocean beneath its icy mantle.

If true, it is possible that this ocean could harbor microbial extraterrestrial life, similar to what has been proposed about Mars, Titan, Europa and Enceladus. It has further been hypothesized that ejecta from Ceres could have sent microbes to Earth in the past.

Other possible surface constituents include iron-rich clay minerals (cronstedtite) and carbonate minerals (dolomite and siderite), which are common minerals in carbonaceous chondrite meteorites. The surface of Ceres is relatively warm, with the maximum temperature estimated to reach approximately 235 K (-38 °C, -36 °F) when the Sun is overhead.

Assuming the presence of sufficient antifreeze (such as ammonia), the water ice would become unstable at this temperature. Therefore, it is possible that Ceres may have a tenuous atmosphere caused by outgassing from water ice on the surface. The detection of significant amounts of hydroxide ions near Ceres’ north pole, which is a product of water vapor dissociation by ultraviolet solar radiation, is another indication of this.

However, it was not until early 2014 that several localized mid-latitude sources of water vapor were detected on Ceres. Possible mechanisms for the vapor release include sublimation from exposed surface ice (as with comets), cryovolcanic eruptions resulting from internal heat, and subsurface pressurization. The limited amount of data suggests that the vaporization is more consistent with cometary-style sublimation.

Origin:

Multiple theories exist as to the origin of Ceres. On the one hand, it is widely believed that Ceres is a surviving protoplanet which formed 4.57 billion year ago in the Asteroid Belt. Unlike other inner Solar System protoplanets, Ceres neither merged with others to form a terrestrial planet and avoided being ejected from the Solar System by Jupiter. However, there is an alternate theory that proposes that Ceres formed in the Kuiper belt and later migrated to the asteroid belt.

The geological evolution of Ceres is dependent on the heat sources that were available during and after its formation, which would have been provided by friction from planetesimal accretion and decay of various radionuclides. These are thought to have been sufficient to allow Ceres to differentiate into a rocky core and icy mantle soon after its formation. This icy surface would have gradually sublimated, leaving behind various hydrated minerals like clay minerals and carbonates.

Today, Ceres appears to be a geologically inactive body, with a surface sculpted only by impacts. The presence of significant amounts of water ice in its composition is what has led scientists to the possible conclusion that Ceres has or had a layer of liquid water in its interior.

Exploration:

Until recently, very few direct observations had been made of Ceres and little was known about its surface features. In 1995, the Hubble Space Telescope captured high-resolutions images that showed a dark spot in the surface that was thought to be a crater – and nicknamed “Piazzi” after its founder.

The near-infrared images taken by the Keck telescope in 2002 showed several bright and dark features moving with Ceres’s rotation. Two of the dark features had circular shapes and were presumed to be craters. One was identified as the “Piazzi” feature, while the other was observed to have a bright central region. In 2003 and 2004, visible-light images were taken by Hubble during a full rotation that showed 11 recognizable surface features, the natures of which are yet undetermined.

With the launch of the Dawn mission, with which NASA intends to conduct a nearly decade-long study of Ceres and Vesta, much more has been learned about this dwarf planet. For instance, after achieving orbit around the asteroid in March of 2015, Dawn revealed a large number of surface craters with low relief, indicating that they mark a relatively soft surface, most likely made of water ice.

Several bright spots have also been observed by Dawn, the brightest of which (“Spot 5”) is located in the middle of an 80 km (50 mi) crater called Occator. These bright features have an albedo of approximately 40% that are caused by a substance on the surface, possibly ice or salts, reflecting sunlight. A haze periodically appears above Spot 5, supporting the hypothesis that some sort of outgassing or sublimating ice formed the bright spots.

The Dawn spacecraft also noted the presence of a towering 6 kilometer-tall mountain (4 miles or 20,000 feet) in early August, 2015. This mountain, which is roughly pyramidal in shape and protrudes above otherwise smooth terrain, appears to be the only mountain of its kind on Ceres.

Like so many celestial bodies in our Solar System, Ceres is a mystery that scientists and astronomers are working to slowly unravel. In time, our exploration of this world will likely teach us much about the history and evolution of our Solar System, and may even lead to the discovery of life beyond Earth.

We have many interesting articles on Ceres here at Universe Today. For example, here are some articles on the many bright spots captured by the Dawn probe, and what they likely are.

And here are some articles on the Asteroid Belt and Why it Isn’t a Planet.

For more information, check out NASA’s Dawn – Ceres and Vesta and Dwarf Planets: Overview.

August 8, 2015December 23, 2015 by Ken Kremer

Mysterious Bright Spots and Pyramidal Mountain Star in Dawn’s Daunting Flyover of Ceres: Video

The intriguing brightest spots on Ceres lie in a crater named Occator, which is about 60 miles (90 kilometers) across and 2 miles (4 kilometers) deep. Vertical relief has been exaggerated by a factor of five. Exaggerating the relief helps scientists understand and visualize the topography much more easily, and highlights features that are sometimes subtle. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/LPI

Video caption: Take a tour of weird Ceres! Visit a 2-mile-deep crater and a 4-mile-tall mountain in the video narrated by mission director Marc Rayman. Get your red/blue glasses ready for the finale – a global view of the dwarf planet in 3D. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/LPI/PSI

Mysterious bright spots and a pyramidal shaped mountain star in a daunting new flyover video of dwarf planet Ceres created from imagery gathered by NASA’s history making Dawn mission – the first ever to visit any dwarf planet which simultaneously ranks as the largest world in the main asteroid belt residing between Mars and Jupiter.

Ceres was nothing more than a fuzzy blob to humankinds most powerful telescopes like the Hubble Space Telescope (HST), until the probe swooped in this year and achieved orbit on March 6, 2015.

The newly released, stunning video takes takes you on a tour like none before for a global cruise over the most fascinating features on Ceres – including the 2-mile-deep (4-km-deep) crater dubbed Occator and a towering 4-mile-tall (6 kilometer-tall) mountain as tall as any in North America.

The spectacular flyover animation was generated from high resolution images taken by Dawn’s framing camera during April and May and is narrated by Marc Rayman, Dawn Chief Engineer and Mission Director of NASA’s Jet Propulsion Laboratory, Pasadena, California.

The video concludes with a 3D view, so you’ll need to whip out your handy red/blue glasses for the finale – a global view of the dwarf planet in 3D.

From the orbital altitude at that time ranging from about 8,400 miles (13,600 kilometers) to 2,700 miles (4,400 kilometers), the highest-resolution regions on Ceres have a resolution of 1,600 feet (480 meters) per pixel.

Pockmarked Ceres is an alien world unlike any other in our solar system, replete with unexplained bright spots and craters of many sizes, large and small.

Occatur has captured popular fascination world-wide because the 60 miles (90 kilometers) diameter crater is rife with a host of the bodies brightest spots and whose nature remains elusive to this day, nearly half a year after Dawn arrived in orbit this past spring.

“Now, after a journey of 3.1 billion miles (4.9 billion kilometers) and 7.5 years, Dawn calls Ceres, home,” says Rayman.

The crater is named after the Roman agriculture deity of harrowing, a method of pulverizing and smoothing soil.

Dawn is an international science mission managed by NASA and equipped with a trio of science instruments from the US, Germany and Italy. The framing camera was provided by the Max Planck Institute for Solar System Research, Göttingen, Germany and the German Aerospace Center (DLR).

The visible and infrared mapping spectrometer (VIR), provided by Italy is an imaging spectrometer that examines Ceres in visible and infrared light.

Dawn’s science team is using the instruments to investigate the light reflecting from Occator at different wavelengths.

From a distance, the crater appeared to be home to a duo of bright spots that looked like a pair of eyes. As Dawn moves ever closer, they became more resolved and now are split into dozens of smaller bright spots.

Global view of Ceres uses data collected by NASA's Dawn mission in April and May 2015. The highest-resolution parts of the map have a resolution of 1,600 feet (480 meters) per pixel. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/LPI/PSI — Global view of Ceres uses data collected by NASA’s Dawn mission in April and May 2015. The highest-resolution parts of the map have a resolution of 1,600 feet (480 meters) per pixel. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/LPI/PSI

Although some early speculation centered on the spots possibly being consistent with water ice or salts, newly gathered data “has not found evidence that is consistent with ice. The spots’ albedo -¬ a measure of the amount of light reflected -¬ is also lower than predictions for concentrations of ice at the surface,” according to the scientists.

“The science team is continuing to evaluate the data and discuss theories about these bright spots at Occator,” said Chris Russell, Dawn’s principal investigator at the University of California, Los Angeles, in a statement.

“We are now comparing the spots with the reflective properties of salt, but we are still puzzled by their source. We look forward to new, higher-resolution data from the mission’s next orbital phase.”
Occator lies in Ceres northern hemisphere.

The huge pyramidal mountain lies farther to the southeast of Occator – at 11 degrees south, 316 degrees east.

Based on the latest calculations, the mountain sits about 4 miles (6 kilometers) high, with respect to the surface around it. That make it roughly the same elevation as Mount McKinley in Denali National Park, Alaska, the highest point in North America.

Among the highest features seen on Ceres so far is a mountain about 4 miles (6 kilometers) high, which is roughly the elevation of Mount McKinley in Alaska's Denali National Park. Vertical relief has been exaggerated by a factor of five to help understand the topography. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/LPI — Among the highest features seen on Ceres so far is a mountain about 4 miles (6 kilometers) high, which is roughly the elevation of Mount McKinley in Alaska’s Denali National Park. Vertical relief has been exaggerated by a factor of five to help understand the topography. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/LPI

The Texas-sized world is slightly smaller than previously thought. Based on new measurements from Dawn, Ceres’ average diameter to 584 miles (940 kilometers), compared to earlier estimates of 590 miles (950 kilometers).

Dawn made history in March when it simultaneously became the first probe from Earth to reach Ceres as well as the first spacecraft to orbit two extraterrestrial bodies.

It had previously visited Vesta. After achieving orbit in July 2011, Dawn became the first spacecraft from Earth to orbit a body in the main Asteroid Belt.

In sharp contrast to rocky Vesta, Ceres is an icy world.

Scientists believe that Ceres may harbor an ocean of subsurface liquid water as large in volume as the oceans of Earth below a thick icy mantle despite its small size – and thus could be a potential abode for life. Overall Ceres is estimated to be about 25% water by mass.

“We really appreciate the interest in our mission and hope they are as excited as we have been about these scientific surprises,” Russell told Universe Today.

“Since we are only just beginning our investigation, I expect that there will be more surprises. So please stick with us!”

As Dawn spirals down to a lower orbit of about 1,200 miles (1,900 km) above Ceres (and then even lower) using its ion engines, new answers and new mysteries are sure to be forthcoming.

“There are many other features that we are interested in studying further,” said Dawn science team member David O’Brien, with the Planetary Science Institute, Tucson, Arizona.

“These include a pair of large impact basins called Urvara and Yalode in the southern hemisphere, which have numerous cracks extending away from them, and the large impact basin Kerwan, whose center is just south of the equator.”

The mission is expected to last until at least June 2016 depending upon fuel reserves.

Dawn was launched on September 27, 2007 by a United Launch Alliance (ULA) Delta II Heavy rocket from Space Launch Complex-17B (SLC-17B) at Cape Canaveral Air Force Station, Florida.

Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.

Ken Kremer

January 20, 2015December 23, 2015 by Nancy Atkinson

First Hubble and Now Dawn Have Seen This White Spot on Ceres. What is it?

There’s a big white spot on Ceres and we don’t know what it is. We’ve known about the white spot since the Hubble Space Telescope first captured images of it in 2003 and 2004, and in subsequent images taken by Hubble, the spot remains visible. Now, in images released yesterday from the Dawn spacecraft, currently on approach to Ceres, the spot remains. In the animated image, below, the spot almost seems to glint in the sunlight.

What is it?

Animation of Ceres made from Dawn images acquired on Jan. 13, 2015 (Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI)

One of the most anticipated aspects the Dawn spacecraft being in orbit around Ceres HAS to be finding out what this spot is. It could be ice, it could be a cryovolcano or geysers, or it could be something else. But we do know fairly certain that it is a real feature and not an image artifact, since it shows up in most of the recent Hubble images and now the Dawn images.

Planetary scientists have long suspected that water ice may be buried under Cere’s crust. A few things point to subsurface ice: the density of Ceres is less than that of the Earth’s crust, and because the surface bears spectral evidence of water-bearing minerals. Scientists estimate that if Ceres were composed of 25 percent water, it may have more water than all the fresh water on Earth. Ceres’ water, unlike Earth’s, would be in the form of water ice and located in the mantle, which wraps around the asteroid’s solid core.

And then last year, the Herschel space telescope discovered water vapor around Ceres, and the vapor could be emanating from water plumes — much like those that are on Saturn’s moon Enceladus – or it could be from cryovolcanism from geysers or icy volcanoes. Without huge a planet or satellite nearby tugging on it, the mechanism for how Ceres is active is also intriguing.

Images from the Hubble Space Telescope in 2004 of Ceres. Credit: NASA/Hubble.

Some scientists also think Ceres may have an ocean and possibly an atmosphere.

As we discussed in our article yesterday, with all that water potentially at Ceres, could it theoretically host microbial life? Some scientists have hinted that Ceres and other icy bodies could be a possible source for life on Earth, another intriguing proposition.

Yesterday, I asked Dawn scientist Paul Schenk what other factors would have to be present in order for microbial life to have arisen on Ceres.

“The presence of carbon molecules is often regarded as necessary for life,” he replied, “and we think we see that on the surface spectroscopically in the form of carbonates and clays. So, I think the questions will be, whether there is actually liquid water of any kind, whether the carbon compounds are just a surface coating or in the interior, and whether Ceres has ever been warm. If those are true then some sort of prebiotic or biotic activity is in play.”

And we’ll soon find out more about this intriguing dwarf planet.

This processed image, taken Jan. 13, 2015, shows the dwarf planet Ceres as seen from the Dawn spacecraft. The image hints at craters on the surface of Ceres. Dawn's framing camera took this image at 238,000 miles (383,000 kilometers) from Ceres. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA — This processed image, taken Jan. 13, 2015, shows the dwarf planet Ceres as seen from the Dawn spacecraft. The image hints at craters on the surface of Ceres. Dawn’s framing camera took this image at 238,000 miles (383,000 kilometers) from Ceres. Credit:
NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

As the deputy principal investigator for Dawn, Carol Raymond said following the Herschel water vapor discovery, “We’ve got a spacecraft on the way to Ceres, so we don’t have to wait long before getting more context on this intriguing result, right from the source itself.”

NASA says that Dawn’s images will surpass Hubble’s resolution at the next imaging opportunity, which will be at the end of January.

The spacecraft arrives at Ceres on March 6, when it will be captured into orbit. The images will continue to improve as the spacecraft spirals closer to the surface during its 16-month study of the dwarf planet. Dawn will eventually be about 1,000 times closer to Ceres than it was for the images released yesterday and therefore will provide 1,000 times as much detail. Dawn at Ceres is primarily a mapping mission, so it will map the geology and chemistry of the surface in high resolution.

It should reveal the processes that drive the outgassing activity, and it should reveal how much water this dwarf planet holds.

And it should reveal the mystery of that white spot.

November 19, 2014December 23, 2015 by Matt Williams

Amazingly Detailed New Maps of Asteroid Vesta

Vesta is one of the largest asteroids in the Solar System. Comprising 9% of the mass in the Asteroid Belt, it is second in size only to the dwarf-planet Ceres. And now, thanks to data obtained by NASA’s Dawn spacecraft, Vesta’s surface has been mapped out in unprecedented detail.
These high-resolution geological maps reveal the variety of Vesta’s surface features and provide a window into the asteroid’s history.

“The geologic mapping campaign at Vesta took about two-and-a-half years to complete, and the resulting maps enabled us to recognize a geologic timescale of Vesta for comparison to other planets,” said David Williams of Arizona State University.

Geological mapping is a technique used to derive the geologic history of a planetary object from detailed analysis of surface morphology, topography, color and brightness information. The team found that Vesta’s geological history is characterized by a sequence of large impact events, primarily by the Veneneia and Rheasilvia impacts in Vesta’s early history and the Marcia impact in its late history.

The geologic mapping of Vesta was made possible by the Dawn spacecraft’s framing camera, which was provided by the Max Planck Institute for Solar System Research of the German Max Planck Society and the German Aerospace Center. This camera takes panchromatic images and seven bands of color-filtered images, which are used to create topographic models of the surface that aid in the geologic interpretation.

A team of 14 scientists mapped the surface of Vesta using Dawn data. The study was led by three NASA-funded participating scientists: Williams; R. Aileen Yingst of the Planetary Science Institute; and W. Brent Garry of the NASA Goddard Spaceflight Center.

This high-res geological map of Vesta is derived from Dawn spacecraft data. Brown colors represent the oldest, most heavily cratered surface. Credit: NASA/JPL-Caltech/ASU — *This high-res geological map of Vesta is derived from Dawn spacecraft data. Credit: NASA/JPL-Caltech/ASU*

The brown colored sections of the map represent the oldest, most heavily cratered surface. Purple colors in the north and light blue represent terrains modified by the Veneneia and Rheasilvia impacts, respectively. Light purples and dark blue colors below the equator represent the interior of the Rheasilvia and Veneneia basins. Greens and yellows represent relatively young landslides or other downhill movement and crater impact materials, respectively.

The map indicates the prominence of impact events – such as the Veneneia, Rheasilvia and Marcia impacts, respectively – in shaping the asteroid’s surface. It also indicates that the oldest crust on Vesta pre-dates the earliest Veneneia impact. The relative timescale is supplemented by model-based absolute ages from two different approaches that apply crater statistics to date the surface.

“This mapping was crucial for getting a better understanding of Vesta’s geological history, as well as providing context for the compositional information that we received from other instruments on the spacecraft: the visible and infrared (VIR) mapping spectrometer and the gamma-ray and neutron detector (GRaND),” said Carol Raymond, Dawn’s deputy principal investigator at NASA’s Jet Propulsion Laboratory in Pasadena, California.

The objective of NASA’s Dawn mission is to characterize the two most massive objects in the main asteroid belt between Mars and Jupiter – Vesta and the dwarf planet Ceres.

These Hubble Space Telescope images of Vesta and Ceres show two of the most massive asteroids in the asteroid belt, a region between Mars and Jupiter. Credit: NASA/European Space Agency — *These Hubble Space Telescope images of Vesta and Ceres show two of the most massive asteroids in the asteroid belt. Credit: NASA/European Space Agency*

Asteroids like Vesta are remnants of the formation of the solar system, giving scientists a peek at its early history. They can also harbor molecules that are the building blocks of life and reveal clues about the origins of life on Earth. Hence why scientists are eager to learn more about its secrets.

The Dawn spacecraft was launched in September of 2007 and orbited Vesta between July 2011 and September 2012. Using ion propulsion in spiraling trajectories to travel from Earth to Vesta, Dawn will orbit Vesta and then continue on to orbit the dwarf planet Ceres by April 2015.

The high resolution maps were included with a series of 11 scientific papers published this week in a special issue of the journal Icarus. The Dawn spacecraft is currently on its way to Ceres, the largest object in the asteroid belt, and will arrive at Ceres in March 2015.

Herschel Discovers Water Vapor Spewing from Ceres

Artist’s impression of Ceres. Credit: ESA.

With the Dawn spacecraft now heading towards the dwarf planet/asteroid Ceres, the mission has suddenly gotten even more intriguing. The Herschel space observatory has discovered water vapor around Ceres, and the vapor could be emanating from water plumes — much like those that are on Saturn’s moon Enceladus – or it could be from cryovolcanism from geysers or icy volcano.

“This is the first time water vapor has been unequivocally detected on Ceres or any other object in the asteroid belt and provides proof that Ceres has an icy surface and an atmosphere,” said Michael Küppers of ESA in Spain, lead author of a paper in the journal Nature.

Ceres might be considered to have a bit of an identity crisis, and this new discovery might complicate things even more. When it was discovered in 1801, astronomers thought it was a planet orbiting between Mars and Jupiter. Later, other bodies with similar orbits were found, marking the discovery of our Solar System’s main belt of asteroids.

Ceres laid claim as the largest asteroid in our Solar System, but in 2006, the International Astronomical Union reclassified Ceres as a dwarf planet because of its large size.

But now, could Ceres also have comet-like attributes? Herschel scientists say the most straightforward explanation of the water vapor production is through sublimation, where ice is warmed and transformed directly into gas, dragging the surface dust with it, and exposing fresh ice underneath to sustain the process. This is how comets work.

Ceres is roughly 950 kilometers (590 miles) in diameter. The best guess on Ceres composition is that it is layered, perhaps with a rocky core and an icy outer mantle. Ice had been theorized to exist on Ceres but had not been detected conclusively, until now.

This graph shows variability in the intensity of the water absorption signal detected at Ceres by the Herschel space observatory on March 6, 2013. Credit: ESA.

Herschel used its far-infrared vision with the HIFI instrument to see a clear spectral signature of the water vapor. But, interestingly, Herschel did not see water vapor every time it looked. There were variations in the water signal during the dwarf planet’s 9-hour rotation period. The telescope spied water vapor four different times, on one occasion there was no signature. The astronomers deduced that almost all of the water vapor was seen to be coming from just two spots on the surface.

Although Herschel was not able to make a resolved image of Ceres, the team was able to derive the distribution of water sources on the surface.

“We estimate that approximately 6 kg of water vapour is being produced per second, requiring only a tiny fraction of Ceres to be covered by water ice, which links nicely to the two localised surface features we have observed,” says Laurence O’Rourke, Principal Investigator for the Herschel asteroid and comet observation programme called MACH-11, and second author on the paper.

The two emitting regions are about 5% darker than the average on Ceres. Since darker regions are able to absorb more sunlight, they are then likely the warmest regions, resulting in a more efficient sublimation of small reservoirs of water ice, the team said.

They added that this new finding could have significant implications for our understanding of the evolution of the Solar System.

“Herschel’s discovery of water vapour outgassing from Ceres gives us new information on how water is distributed in the Solar System,” said Göran Pilbratt, ESA’s Herschel Project Scientist. “Since Ceres constitutes about one fifth of the total mass of asteroid belt, this finding is important not only for the study of small Solar System bodies in general, but also for learning more about the origin of water on Earth.”

Dawn is scheduled to arrive at Ceres in the spring of 2015 after spending more than a year orbiting the large asteroid Vesta. Dawn will give us the closest look ever at Ceres surface and provide more insight into this latest finding.

“We’ve got a spacecraft on the way to Ceres, so we don’t have to wait long before getting more context on this intriguing result, right from the source itself,” said Carol Raymond, the deputy principal investigator for Dawn. “Dawn will map the geology and chemistry of the surface in high resolution, revealing the processes that drive the outgassing activity.”

Sources: ESA, NASA, Nature

September 12, 2013April 26, 2016 by Elizabeth Howell

This Is What It Looks Like Hovering Above An Asteroid

An atlas of the asteroid, Vesta, created from mosaics of 10 000 images from Dawn’s framing camera (FC) instrument, taken during the Dawn Mission’s Low Altitude Mapping Orbit (LAMO) an altitude of around 135 miles (210 kilometres). Credit: European Space Agency

Now’s your big chance to get up close and personal with Vesta, one of the largest asteroids in the solar system.

A new atlas has been released based on 10,000 images from the Dawn mission‘s framing camera instrument, which took the pictures from an average altitude of about 131 miles (210 kilometers). Each map has a scale of 1 centimetre to 2 kilometres (roughly a scale of 0.4 inches : 1.2 miles).

“Creating the atlas has been a painstaking task – each map sheet of this series has used about 400 images,” stated Thomas Roatsch, who is with the German Aerospace Center (DLR) Institute of Planetary Research and led the work.

This image from NASA’s Dawn spacecraft shows a close up of part of the rim around the crater Canuleia on the giant asteroid Vesta. Canuleia, about 6 miles (10 kilometers) in diameter, is the large crater at the bottom-left of this image. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/PSI/Brown — This image from NASA’s Dawn spacecraft shows a close up of part of the rim around the crater Canuleia on the giant asteroid Vesta. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/PSI/Brown

“The atlas shows how extreme the terrain is on such a small body as Vesta. In the south pole projection alone, the Severina crater contours reaches a depth of 18 kilometres [11 miles]; just over 100 kilometres [62 miles] away the mountain peak towers 7 kilometres [4.3 miles] above the … reference level.”

You can check out the raw atlas images at this website. The research was presented at the European Planetary Science Conference and also published Sept. 1 at Planetary and Space Science.

Interested in getting involved in Vesta asteroid mapping yourself? A initiative called AsteroidMappers is open to amateur enthusiasts; check out more details in this past Universe Today story.

Source: European Planetary Science Conference

March 29, 2013December 23, 2015 by Elizabeth Howell

5 Weird Things About Vesta

An impact structure on asteroid Vesta resembling a snowman. Credit: NASA

When Heinrich Wilhelm Olbers first glimpsed Vesta on March 29, 1807 — this date in history — the asteroid was but a small point of light. Asteroid science was very, very new at the time as the first asteroid (Ceres) had been discovered only six years before.

Fast-forward 200-plus years and we can treat Vesta as a little world in its own right. NASA sent the Dawn spacecraft in orbit for about a year, which has produced a wealth of weird results. (Stay tuned for what happens at Dawn’s next port of call: Ceres.)

Below are five strange things we’ve discovered about Vesta:

1) Vesta has a fresh face.

Space “weathering” from tiny particles hitting the Moon has shaped the surface over time. Not so much on Vesta. It turns out the topography on the asteroid (and other factors) allow constant mixing of the surface, making it appear almost new even though the asteroid is several billion years old. “Vesta ‘dirt’ is very clean, well mixed and highly mobile,” said Carle Pieters, one of the lead authors and a Dawn team member based at Brown University, Providence, R.I. when the finding was made public.

2) Vesta might have stretch marks.

Dawn image of Vesta showing its nearly circumferential equatorial grooves (NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)

While trying to wrap their mind around fault lines that circle Vesta’s equator, a group of scientists proposed these could be graban — features that show surface expansion. It’s possible these faults came to be after something big smashed into the planet, creating a gigantic crater with a peak that is almost three times as high as Mt. Everest. The expansion occurred as Vesta’s interior differentiated, or experienced a separation of its core, mantle and crust.

3) Vesta kind of looks like a planet.

'Rainbow-Colored Palette' of Southern Hemisphere of Asteroid Vesta from NASA Dawn Orbiter. This mosaic using color data obtained by the framing camera aboard NASA's Dawn spacecraft shows Vesta's southern hemisphere in false color, centered on the Rheasilvia impact basin, about 290 miles (467 kilometers) in diameter with a central mound reaching about 14 miles (23 kilometers) high. The black hole in the middle is data that have been omitted due to the angle between the sun, Vesta and the spacecraft. The green areas suggest the presence of the iron-rich mineral pyroxene or large-sized particles. This mosaic was assembled using images obtained during Dawn's approach to Vesta, at a resolution of 480 meters per pixel. The German Aerospace Center and the Max Planck Institute for Solar System Research provided the Framing Camera instrument and funding as international partners on the mission team. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA — ‘Rainbow-Colored Palette’ of Southern Hemisphere of Asteroid Vesta from NASA Dawn Orbiter. This mosaic using color data obtained by the framing camera aboard NASA’s Dawn spacecraft shows Vesta’s southern hemisphere in false color, centered on the Rheasilvia impact basin, about 290 miles (467 kilometers) in diameter with a central mound reaching about 14 miles (23 kilometers) high. The black hole in the middle is data that have been omitted due to the angle between the sun, Vesta and the spacecraft. The green areas suggest the presence of the iron-rich mineral pyroxene or large-sized particles. This mosaic was assembled using images obtained during Dawn’s approach to Vesta, at a resolution of 480 meters per pixel. The German Aerospace Center and the Max Planck Institute for Solar System Research provided the Framing Camera instrument and funding as international partners on the mission team. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Looking at Vesta in false color — wavelengths that let different kinds of minerals shine — show a veritable cornucopia of different types of stuff. There’s the iron-rich mineral pyroxene, there’s diagenite material (characteristic of stony meteorites), and various particles of different sizes and ages. “Vesta is a transitional body between a small asteroid and a planet and is unique in many ways,” said mission scientist Vishnu Reddy of the Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany. “We do not know why Vesta is so special.”

4) Vesta has hydrogen.

Hydrated minerals are circling the equator of the little world. It’s not quite water, but still an interesting find for scientists. “The source of the hydrogen within Vesta’s surface appears to be hydrated minerals delivered by carbon-rich space rocks that collided with Vesta at speeds slow enough to preserve their volatile content,” stated Thomas Prettyman, lead scientist for Dawn’s gamma ray and neutron detector (GRaND) from the Planetary Science Institute.

5) The northern and southern hemispheres look completely different.

Shaded-relief topographic map of Vesta southern hemisphere showing two large impact basins - Rheasilvia and Older Basin. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA — Shaded-relief topographic map of Vesta southern hemisphere showing two large impact basins – Rheasilvia and Older Basin.
Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

It’s fun to get to a new world and end up with something fundamentally surprising. Some of the very first pictures of Vesta showed a vast difference between different regions of the planet, giving scientists a workout in terms of figuring out how that came to be. “The northern hemisphere is older and heavily cratered in contrast to the brighter southern hemisphere where the texture is more smooth and there are lots of sets of grooves. There is a massive mountain at the South Pole. One of the more surprising aspects is the set of deep equatorial troughs,” said Carol Raymond, Dawn deputy principal investigator, of NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

Here’s a video where you can see that for yourself:

July 12, 2012April 13, 2022 by Ken Kremer

Dawn’s Vestan Endeavour Exceptionally Exciting near End of Year-Long Super Science Survey

Image Caption: Divalia Fossa equatorial trough at Vesta pictured in side by side images showing apparent brightness and topography. The trough encircles most of Vesta and is located just south of the equator. It is about 10 kilometers (6 miles) wide. Rubria and Occia craters straddle Divalia Fossa. The image was snapped on Oct 16, 2011 from an altitude of 700 km (435 mi) from the HAMO mapping orbit. Image Credit: NASA/ JPL-Caltech/ UCLA/ MPS/ DLR/ IDA

“NASA’s Dawn mission to Asteroid Vesta is going exceptionally well”, Dr. Marc Rayman, the mission’s Chief Engineer, told Universe Today in an exclusive interview as the revolutionary spacecraft nears the end of its more than 1 year long super science survey orbiting the giant space rock.

“The Dawn mission is not only going better than we had expected but even better than we had hoped.”

Dawn is Earth’s first mission ever to orbit and explore Vesta up close.

“We have acquired so much more data than we had planned even in late 2011! We have conducted a tremendous exploration of Vesta – the second most massive body between Mars and Jupiter, a giant of the main asteroid belt.”

“Now we are in our second high altitude mapping orbit (HAMO2), which is the final intensive campaign of the Vesta mission,” Rayman told me.

Image Caption: Dawn Orbiting Vesta above the “Snowman” craters. This artist’s concept shows NASA’s Dawn spacecraft orbiting the giant asteroid Vesta above the Snowman craters. The depiction of Vesta is based on images obtained by Dawn’s framing cameras. Dawn is an international collaboration of the US, Germany and Italy. Credit: NASA/JPL-Caltech

Indeed Dawn’s science and maneuvering endeavour’s at Vesta have proceeded so flawlessly that NASA has granted the science team a bonus of 40 days additional time in orbit split between the lower and higher science orbits known as LAMO and HAMO or the Low Altitude Mapping Orbit and the High Altitude Mapping Orbit respectively.

“Our original Vesta departure date was July 17, and now it is about August 26.” Rayman explained.

The bonus time at LAMO has already been completed. Now the team is about to begin the bonus time at HAMO – consisting of two additional mapping cycles beyond the four originally planned.

Each mapping cycle in HAMO2 consists of 10 orbits. Each orbit is about 12.5 hours.

“On July 14, we will complete mapping cycle 4 and begin 5 (of 6). On July 25 we will leave HAMO2 and escape from orbit on August 26. We will stop thrusting several times before escape to take more neat pictures, mostly of the northern hemisphere,” Rayman told me.

“As Dawn revolves, Vesta rotates on its axis beneath it, turning once every 5.3 hours.”

When Dawn arrived in orbit at Vesta in July 2011 the northern polar region was in darkness as the southern hemisphere basked in summer’s glow. Now as Dawn departs Vesta in August, virtually all of the previously unseen and unphotographed northern polar region is illuminated and will be mapped in exquisite detail.

Coincidentally on July 13/14 as HAMO2 Cycle 4 ends, I’ll be presenting a free public lecture about Dawn and NASA’s Planetary and Human Spaceflight programs at the Adirondack Public Observatory.

Image Caption: Asteroid Vesta and Mysterious Equatorial Grooves – from Dawn Orbiter. This full view of the giant asteroid Vesta was taken by NASA’s Dawn spacecraft on July 24, 2011, at a distance of 3,200 miles (5,200 kilometers). This view shows impact craters of various sizes and mysterious grooves parallel to the equator. The resolution of this image is about 500 meters per pixel. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Why has Dawn been granted an extended mission ?

“Dawn has gone so well that we had consumed not even one day of our 40 days of operations margin,” Rayman stated .

“That allowed us to spend more time in LAMO. We had had some unexpected events to be sure, but we managed to deal with all of them so expeditiously that the entire margin remained intact. Then we received the (entirely unrelated) 40 day extension, which allowed us to leave Vesta later. That came about because of our being able to shorten the flight from Vesta to Ceres, so we could still reach Ceres on schedule in 2015.”

“That 40 days allowed us to spend still ~ 30 more days in LAMO and increase HAMO2 by 10 days to a total of six cycles. We got still more time by finding ways to make the trip from HAMO2 to escape a little more efficiently, and that’s what allowed HAMO2 to be even longer, with the additional eight days of VIR-only observations I described in my most recent Dawn Journal.”

“The summary is that every investigation has been more productive than we could have imagined, and because the exploration of Vesta has gone so well, we have been able to apply our unused margin to get even more out of the mission. It is very very gratifying and exciting.”

So we have a few more weeks to enjoy the wondrous sights of Vesta before Dawn fires up her revolutionary ion thrusters to escape the gravitational tug of Vesta and head off to the dwarf planet Ceres, the largest asteroid in the main belt of our Solar System – and which some have speculated may hold vast caches of water and perhaps even liquid oceans suitable for sustaining life.

Ken Kremer

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July 13/14: Free Public Lectures about NASA’s Mars, Vesta and Planetary Exploration, the Space Shuttle, SpaceX , Orion and more by Ken Kremer at the Adirondack Public Observatory in Tupper Lake, NY.

May 10, 2012January 7, 2016 by Nancy Atkinson

Fly Over Vesta’s Cratered Terrain with Dawn

I’ve been waiting for nearly two months to be able to share these videos from the Dawn mission’s “flyover” views of Vesta. Scientists showed some of these incredible views at the Lunar and Planetary Science Conference in March, but couldn’t make them public until they published their work in the journal Science.

“Vesta is unlike any other object we’ve visited in the solar system,” said Dawn mission team member Vishnu Reddy at a briefing today. “We see a wide range of variation on the surface, with some areas bright as snow, and other areas as dark as coal.”

The video above is a stunningly beautiful flyover of most of Vesta. Another video, below, takes viewers on a virtual tour of Vesta’s south polar basin, the ‘snowman’ set of craters and a crater called Oppia.

Scientists said today that Vesta more closely resembles a small planet or Earth’s Moon than another asteroid, and they now have a better understanding of both Vesta’s surface and interior, and can conclusively link Vesta with meteorites that have fallen on Earth.

Continue reading “Fly Over Vesta’s Cratered Terrain with Dawn”